Abstract
A method for quantitative assessment of grinding burns is developed on the basis of digital technology. It is tested in conditions of pendulum grinding of hardened parts made of steel 37Khr4 by abrasive wheels of different porosity: 25AF46L10V5KF35 (i=1), 25AF46M12V5PO3 (i=2), EKE46K3V (i=3), 5A46L10VAX (i=4). Abrasive wheels with i=1;2 relate to high-porous wheels, while the abrasive wheels with i=3;4 are made of monocrystal carborundum and have standard porosity (producer – company Dorfner schleifmittelwerk (Germany)). To confirm the reliability of the proposed methodology for assessing burn marks a study of details microhardness is undertaken. In consideration of grinding stochastic character, statistical methods (particularly – rank): parametric and nonparametric are used to reduce the observations. They give opportunity to evaluate the reliability of decisions as well as the cuttability of wheels not only by the measures of position but by measures of dispersion. The second characteristic of the marginal frequency distribution is more important while grinding of critical parts on adapted machines with manual control for eliminating rejected probability. The statistical results have shown that in the infringements of homoscedasticity and normality of observations’ allocation, the parametric method reduced to dislodgement of measures of position and confidence intervals. A correlation between measures of position for percent burn content and microhardness is established. Tool 25AF46L10V5KF35 grinding with regime: vc = 35 m.s-1, sl = 7 m.min-1, sc = 1 mm.(d.s.)-1, t = 0.015 mm, z=0.15mm secures the greatest microhardness of parts made of steel 37Khr4 in the minimum burns. This investigation has shown that grinding parts by wheels runs in the softening of their surfaces, but no re-hardening burn. The wheel i=2 with pore-forming ПО3 is probably used for decrease of rejected parts.
Keywords: grinding, burns, assessment, microhardness, statistic, mean, median, measure of position, digital technology
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